1. Field of the Invention
The present invention relates to bedding mattresses and cushions having a multi-layer construction comprised of various foam materials for support and comfort. An air blower integrated with the mattress or cushion generates air flow through the mattress or cushion to draw heat and moisture away from a top surface of the mattress or cushion. Such air flow through the mattress or cushion in either direction enhances comfort for person(s) reclining on the mattress or cushion.
2. Background
Poor body alignment on a mattress or cushion can cause body discomfort, leading to frequent body movement or adjustment during sleeping and a poor night's sleep. An ideal mattress has a resiliency over the length of the body reclining thereon to support the person in spinal alignment and without allowing any body part to bottom out. A preferred side-lying spinal alignment of a person on a mattress maintains the spine in a generally straight line and on the same center line as the legs and head. An ideal mattress further has a low surface body pressure over all or most parts of the body in contact with the mattress.
Prolonged contact between body parts and a mattress surface tends to put pressure onto the reclining person's skin. The pressure tends to be greatest on the body's bony protrusions (such as sacrum, hips and heels) where body tissues compress against the mattress surface. Higher compression tends to restrict capillary blood flow, called “ischemic pressure”, which causes discomfort. The ischemic pressure threshold normally is considered to be approximately 40 mmHg. Above this pressure, prolonged capillary blood flow restriction may cause red spots or sores to form on the skin (i.e., “stage I pressure ulcers”), which are precursors to more severe tissue damage (i.e., “stage IV pressure ulcers” or “bed sores”). The preferred pressure against the skin of a person in bed remains generally below the ischemic threshold (e.g., below 40 mmHg, preferably below 30 mmHg).
Body support systems that redistribute pressure, such as mattresses or cushions, frequently are classified as either dynamic or static. Dynamic systems are driven, using an external source of energy (typically direct or alternating electrical current) to alter the level of pressure by controlling inflation and deflation of air cells within the system or the movement of air throughout the system. In contrast, static systems maintain a constant level of air pressure and redistribute pressure through use of materials that conform to body contours of the individual sitting or reclining thereon.
Although foam frequently is used in both static and dynamic body support systems, few, if any, systems incorporate foam to redistribute pressure, withdraw heat, and draw away or evaporate moisture buildup at foam support surfaces. While foam has been incorporated into some body support systems to affect moisture and heat, most of these systems merely incorporate openings or profiles in foam support layers to provide air flow paths. In addition, few, if any, systems specify use of internal air flow guides with specific parameters related to heat withdrawal and moisture evaporation at foam support surfaces (i.e., Heat Withdrawal Capacity and Evaporative Capacity, which may be quantitatively measured). Hence, improvements continue to be sought.
Consumers appreciate the body-supporting characteristics offered by mattress constructions that include viscoelastic (slow recovery) foams. However, viscoelastic foams tend to have lower air flow (breathability), and mattresses constructed with such foams tend to retain heat and moisture. Effective and reasonably priced measures to draw away heat and moisture from reclining surfaces of consumer bedding mattresses and cushions continue to be sought. Effective and reasonably priced measures to cool the reclining surfaces of consumer bedding mattresses and cushions continue to be sought.